Centrifugal pump with thrust balancing means



March 3, 1964 D. WITT ETAL CENTRIFUGAL. PUMP WITH THRUST BALANCING MEANS Filed Dec. 15, 1961 FIG. I

FIG. 2

INVENTORS DONALD L. W/TT RICHARD VAUGHN 6 A TORA'IEYS X A eE-T United States Patent 3,123,010 CENTRIFUGAL PUMP WITH THRUST BALANCING MEANS Donald L. Witt, North Palm Beach, and Richard Vaughn, Lake Park, Fla, assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Dec. 15, 1961, Ser. No. 159,800 1 Claim. (Cl. 103-103) The present invention relates to a centrifugal pump impeller and more particularly to a centrifugal pump impeller having thrust balancing means.

It is well known in the art of centrifugal pumps that during the operation of a single-suction single-stage pump an axial thrust is developed in the direction of the flow of fluid being pumped. These axial forces are the result of the lack of symmetry of single-suction impellers in the axial direction.

As a means of overcoming or counteracting this axial thrust various arrangements of thrust balancing have been heretofore employed. The most obvious way of overcoming this axial thrust would be to employ a double-suction impellerd. By so doing, the thrust developed by each half of the impeller is cancelled out by the axial thrust developed by the other half of the impeller.

However, the pumping requirements of the particular application may not justify the use of a double-suction pump. Therefore it becomes apparent that some other arrangement of overcoming this problem is desired.

In an effort to eliminate these forces in a single-suction pump it has been the practice to employ wearing rings on the rearward side of the impeller. However, if the material being pumped is of a flammable nature care must be taken to avoid any metal to metal contact which is quite possible in the use of wearing rings. Another disadvantage of this type arrangement is the reduced efficiency which may be encountered if the strict tolerance control on the impeller to housing clearances are not properly maintained. Since it is very desirable to have a pump operating at its optimum efliciency it becomes imperative that the clearances between the housing and impeller are kept to a minimum.

An object of the present invention is the provision of a centrifugal pump impeller which could be manufactured without strict tolerances.

Another object is to provide a centrifugal pump impeller which would allow accurate thrust balancing.

A further object of the invention is the provision of a centrifugal pump impeller which employs a plastic insert which is replaceable when worn out.

Still another object of the present invention is to provide a centrifugal pump impeller having an insert which may be fit to a close tolerance by lapping during assembly.

Another object of the present invention is to provide a centrifugal pump impeller which is easy to manufacture and possesses none of the aforedescribed disadvantages of the prior art.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows a longitudinal sectional view of the upper half of a pump illustrating a preferred embodiment of the invention;

FIG. 2 shows a section of the device taken on the line 22 of FIG. 1;

FIG. 3 is an enlarged perspective view of the device illustrating the details of the slot and insert.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1, which illustrates a preferred embodiment, the upper half of a pump 10.

The pump 10 includes a casing having a forward part 11 and a rearward part 12. Rearward part 12 is provided with a flange portion 13 which receives the edge 14 of forward part 11. Both parts 11 and 12 are fixedly secured together by a plurality of bolts 15 through flange 13 into edge 14. A rubber gasket 38 is provided to prevent any leakage at this joint. The forward part 11 of the casing is provided with an inlet opening 16 and is contoured to closely follow the shape of the impeller 17. The peripheral portion of the forward part 11 is provided with an outlet scroll 18 for the discharge of the fluid being pumped.

The rearward part 12 of the casing has a substantially vertical rear wall 19 that terminates at its radially innermost end with an annular recess 21. The inner portion of recess 21 serves as a stufling box and receives the packing 22. The outer portion of recess 21 is threaded at 23 to receive packing gland 24. The impeller 17 is secured to shaft 27 by means of a keyway and key 25 and locking nut 26 which is threaded onto the end of shaft 27. Locking nut 27 is provided with a cap 20 which is of smooth configuration so as to offer as little resistance to the flow of the incoming fluid as possible. In addition, shaft 27 is provided with a taper 30 which mates with the internal taper on impeller 17 and serves to further secure the impeller 17 to shaft 27. The impeller shaft 27 may be driven by any suitable prime mover, none being shown.

Impeller 17 is an open face single-suction impeller which consists of a plurality of vanes 28 that are integral with shroud 29. The impeller 17 is also provided with a hub 31 which surrounds shaft 27 and receives locking key 25. The rearward wall 32 of impeller 17 is provided with an integral rearward channel portion 34. Channel 34 is formed by a pair of spaced walls 33 which are integral with the rearward wall 32 of impeller 17 and extends the entire length thereof. Channel 34 receives plastic insert 35 which is held in position by means of a plurality of pins 36 that enter through holes 37 in the vertical walls 33 and insert 35.

FIG. 2 which is a sectional view of FIG.1 taken along the line 22 clearly illustrates the relationship of the insert 35 with respect to the rearward wall 19 of the casing. As can be seen, insert 35 is in rubbing contact with the wall 19. It can therefore be seen that any axial thrust of the impeller 17 toward the wall 19 will be absorbed by the insert 35 due to its contact with the rearward wall 19. The particular plastic material used is not considered to be a part of the invention. However, the plastic material use must possess certain characteristics such as being of sulhcient rigidity to resist compression. It must also be of sufficient strength to withstand the rubbing contact with the wall 19. In addition, the fluid being pumped must be taken in o consideration when selecting the type of insert to be used. It can readily be seen that certain plastic materials will break down more readily than others when brought into contact with various types of fluids.

FIG. 3 is an enlarged perspective view of a portion of the impeller 17. The vertical walls 33 on the rear wall 32 are also clearly shown. The channel 34 and insert 35 are illustrated with pin 36 for securely fastening the insert 35 in the channel 34. It is to be noted that locking pins 36 are shown as the means for holding insert 35 in its proper positions within channel 34. However, applicant does not wish to be limited to this particular type of fastening since other suitable means may be employed.

The manner in which the pump is assembled is as follows:

Prior to securing the impeller 17 to shaft 27 the forward part 11 of the casing must be removed to permit the im eller 17 to be placed on shaft 27. After the impeller 17 is placed on the shaft 27 the locking key is inserted into the keyway 25 to prevent relative rotation between the impeller 17 and shaft 27. Next, locking nut 26 is threaded onto the shaft 27 urging the impeller 17 into tighter engagement with taper 30 on shaft 27. After the nut 26 is tightened a cap 26 is placed on the end of the shaft 2'7 to protect threaded end of the shaft 27 and to provide an unobstructed flow of incoming fluid.

ifter the impeller 17 is securely mounted on shaft 27 plastic insert 35 may be placed in channel 34 and secured in place by locking pins 36. (It is to be noted that although only one vane 28 and plastic insert 35 is shown, the impeller 1'7 is provided with a plurality of each.) Having secured the inserts 35 to the impeller 17 the next step would be to lap the insert 35 into a close tolerance with the rearward Wall 119 of the casing. After this is don the forward part 11 of the casing may be mated with the rearward part 12 and secured together by means of flange 13 and bolts 15. With the casing secured together and the inlet opening 16 connected to a source of fluid supply the pump is ready for operation.

After an extended period of operation the pump should be disassembled and an inspection made of the clearances between the inserts 35 and the rear wall 19 of the casing. If it is apparent that there is no longer any actual contact between the insert 35 and the wall 19 it is an indication that new inserts 35 should be inserted.

Gbviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

In a centrifugal pump having a casing formed by a first and second section, an inlet opening centrally located in said first section, an outlet opening formed in the periphery of said first section, flange means on said second section for removably securing said first and second sections of said casing together, an aperture centrally located in said second section of said casing, a rotatable shaft extending into said casing through said aperture, an impeller having a hub for engagement with said shaft, securing means comprising a taper on said shaft which mates with a taper on said impeller hub and a locking nut urging said impeller onto said shaft to prevent its separation therefrom, said impeller having a front face and a rear Wall, a plurality of vanes integrally mounted on said front face, a plurality of spaced back vanes arranged in pairs and extending from the hub to the circumference of said impeller, said vanes projecting from said rear wall, a plurality of radial channels formed in said back vanes, an insert replaceably secured in each of said channels, said insert being rectangularin crosssection and conforming to the configuration of the channel which retains it, said insert having a flat outerface which may be lap fitted into a close fit with said inner rearward wall of said casing forits full length.

References Cited in the file of this patent UNITED STATES PATENTS 'Re. 14,988 Parsons Nov. 16, 1920 1,271,072 Parsons July 2, 1918 1,739,604 Monroe Dec. 17, 1929 1,947,148 Andersen Feb. 13, 1934 2,042,533 'Kieser June 2, 1936 2,406,499 'Iandasek Aug. 27, 1946 2,649,050 Didbin Aug. 18, 1953 2,669,938 La Bour Feb. 23, 1954 2,732,021 Taft Jan. 24, 1956 2,848,190 Barr Aug. 19, 1958 3,065,705 Sadler et al. Nov. 27, 1962 FOREIGN PATENTS 453,588 Canada Dec. 28, 1948 

